The invention relates to a laser marker in which a laser beam is channeled or profiled into a printing pattern which is to be marked on the surface of an object, and more particularly, to a pattern controlling device for use in such laser marker.
Generally, a printing pattern in a laser marker of the kind described is obtained by the use of a mask which is provided with areas having a transmittance of zero and areas having a transmittance of unity which define a given pattern. When the mask is placed into the path of passage of the laser beam, the laser beam is channeled into the given pattern and then collected by a condenser lens to irradiate a label applied to the outer surface of a container, for example, thus marking the pattern on the label. In the conventional laser marker, the mask used is usually punched from a thin metal sheet, and is fixedly located in the path of passage of the laser beam. When it is desired to change the pattern to be marked on the label, the mask must be replaced by another which is again punched into a desired configuration. As a consequence, the replacement of the masks and the maintenance of a variety of masks require both time and labor. It is virtually impossible to mark a lot number corresponding to each container or each group of containers on the labels of containers which are being continuously conveyed at a high speed by a conveyor unit because it is difficult to achieve a reliable replacement of the masks.